mm: make page ref count overflow check tighter and more explicit

[mirror_ubuntu-bionic-kernel.git] / include / linux / mm.h

diff --git a/include/linux/mm.h b/include/linux/mm.h
index eba6b0c1378c2ca76dd0594338c45b220a72e770..c3acf6ac6d1013f3099b8c1fd9bf2ac140d44808 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -154,7 +154,7 @@ extern int overcommit_kbytes_handler(struct ctl_table *, int, void __user *,
  * mmap() functions).
  */
 
-struct vm_area_struct *vm_area_alloc(void);
+struct vm_area_struct *vm_area_alloc(struct mm_struct *);
 struct vm_area_struct *vm_area_dup(struct vm_area_struct *);
 void vm_area_free(struct vm_area_struct *);
 
@@ -836,6 +836,10 @@ static inline bool is_device_public_page(const struct page *page)
 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
 
 
+/* 127: arbitrary random number, small enough to assemble well */
+#define page_ref_zero_or_close_to_overflow(page) \
+       ((unsigned int) page_ref_count(page) + 127u <= 127u)
+
 static inline void get_page(struct page *page)
 {
        page = compound_head(page);
@@ -843,7 +847,7 @@ static inline void get_page(struct page *page)
         * Getting a normal page or the head of a compound page
         * requires to already have an elevated page->_refcount.
         */
-       VM_BUG_ON_PAGE(page_ref_count(page) <= 0, page);
+       VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page);
        page_ref_inc(page);
 }
 
@@ -1669,11 +1673,15 @@ int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address);
 
 static inline void mm_inc_nr_puds(struct mm_struct *mm)
 {
+       if (mm_pud_folded(mm))
+               return;
        atomic_long_add(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes);
 }
 
 static inline void mm_dec_nr_puds(struct mm_struct *mm)
 {
+       if (mm_pud_folded(mm))
+               return;
        atomic_long_sub(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes);
 }
 #endif
@@ -1693,11 +1701,15 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address);
 
 static inline void mm_inc_nr_pmds(struct mm_struct *mm)
 {
+       if (mm_pmd_folded(mm))
+               return;
        atomic_long_add(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes);
 }
 
 static inline void mm_dec_nr_pmds(struct mm_struct *mm)
 {
+       if (mm_pmd_folded(mm))
+               return;
        atomic_long_sub(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes);
 }
 #endif
@@ -2398,6 +2410,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
        return vma;
 }
 
+static inline bool range_in_vma(struct vm_area_struct *vma,
+                               unsigned long start, unsigned long end)
+{
+       return (vma && vma->vm_start <= start && end <= vma->vm_end);
+}
+
 #ifdef CONFIG_MMU
 pgprot_t vm_get_page_prot(unsigned long vm_flags);
 void vma_set_page_prot(struct vm_area_struct *vma);